1. Field of the Invention
The present invention relates to phosphate free corrosion-inhibited antifreeze formulations for use in the cooling systems of internal combustion engines. In particular, the invention relates to an anhydrous antifreeze formulation comprised predominantly of propylene glycol, together with borate, molybdate, nitrate, nitrite, tolyltriazole, and silicate.
2. Description of the Prior Art
The use of each of the components employed in the formulations of the present invention is taught in the art.
Propylene glycol is taught as a freezing point depressant in antifreeze formulations, for example in U.S. Pat. Nos. 2,147,409, 4,149,985 and many others.
Alkali metal borates have been used as corrosion-inhibitors in antifreeze formulations. See, for example, U.S. Pat. Nos. 4,149,985, 2,566,923, 3,960,740, 2,373,570, 2,815,328 and the like.
Alkali metal sebacates have been used as corrosion inhibitors in aqueous systems as taught in U.S. Pat. No. 2,726,215, and in antifreeze coolants as taught in U.K. Patent No. 1,004,259 and in U.S. Pat. Nos. 4,382,008, 4,561,990, 4,587,028, 4,588,513 and the like.
Alkali metal molybdates have been taught as corrosion-inhibitors in antifreeze formulations. See U.S. Pat. Nos. 2,147,409 and 4,561,990, for example.
Alkali metal mercaptobenzothiazole has been used in anti-freeze formulations along with other additives. See, for example, U.S. Pat. Nos. 2,815,328, 4,455,248, 4,414,126, 4,545,925 and the like.
Alkali metal nitrates have been added to antifreeze formulations as corrosion-inhibitors. See, for example, U.S. Pat. Nos. 2,815,328, 4,508,684, 4,455,248, 4,587,028 and the like.
Alkali metal nitrites have been added to antifreeze formulations as described, for example, in U.S. Pat. Nos. 4,587,028 and 4,728,452.
Tolyltriazole is taught as an antifreeze formulation component, for example in U.S. Pat. Nos. 4,242,214, 2,587,028, 4,382,008, U.K. Patent 1,004,259 and the like.
In addition, alkali metal silicates are shown as antifreeze components in, for example, U.S. Pat. Nos. 2,815,328, 4,242,214, 4,382,008, 4,382,870, 4,455,248, 4,149,985 and the like.
Alkali metal phosphates have been used as corrosion-inhibiting components of antifreeze formulations as shown, for example, in U.S. Pat. Nos. 2,147,409, 4,382,870, 4,455,248, 4,149,985, 4,545,925 and the like.
A considerable number of patents have been granted which are directed to antifreeze formulations which comprise certain specific combinations of components. Included among such patents are U.S. Pat. Nos. 4,242,214, 4,382,008, 4,382,870, 4,455,248, 4,561,990, 4,587,028, 4,588,513, 4,545,925, 4,000,079, 4,338,209, 4,759,864, 4,219,433 and many others.
A considerable amount of effort has been expended in the development of anhydrous antifreeze formulations and combustion engine cooling configurations which use the same. See U.S. Pat. Nos. 4,550,694 and 4,630,572 as well as "Development of an Anhydrous Coolant for Automotive Applications" by Greg P. Reny and Guy L. Titley of Dow Chemical Canada Inc.
In certain applications such as described, for example, in U.S. Pat. Nos. 4,550,694 and 4,630,572 cited above, the development of anhydrous antifreeze formulations which are used without water dilution is important. Operation using such formulations can be carried out at favorable higher coolant temperatures without the development of excessive pressures.
It should be noted that anhydrous formulations based on ethylene glycol are not suitable due to the freezing characteristics of anhydrous ethylene glycol formulations.